Turkish authorities have taken into custody two foreign nationals at Istanbul's main airport on suspicion of being connected to the New Year’s Eve terrorist attack on a nightclub that killed 39 people.

The two suspects were arrested on Tuesday after they entered the Ataturk International Airport and were then taken to Istanbul’s police headquarters by security officers following interrogation, the local Dogan news agency reported.

The government announced on Monday that eight suspects had been taken into custody. However, authorities were then cited by new outlets as reporting six more arrests in the Anatolian city of Konya, raising the number of detained suspects to 14.

The airport detentions on Tuesday bring to 16 the total number of suspects in custody so far over the nightclub attack.

The key suspect in the terrorist attack, which was claimed by the ISIS terrorist group, remains at large and unidentified as local news outlets reported that he was staying at a rented apartment in Konya prior to going to Istanbul to wage the terror attack.

Although the assailant’s identity is yet unknown, local reports have alleged that he is from Central Asia.

Armed with a long-barreled weapon, he first killed a policeman and a civilian early Sunday outside the club before entering and shooting at some of the nearly 600 people inside.

Daesh has been blamed for at least half a dozen attacks on civilian targets across Turkey in the past 18 months but this is the first instance it has directly claimed responsibility for. It made the claim on one of its Telegram channels, a method used after terror attacks elsewhere.

Meanwhile, Turkish Prime Minister Binali Yildirim blamed Washington for supporting Syria-based Kurdish forces, which Ankara considers to be terrorists, calling on US President-elect Donald Trump to put an end to "this shame."

"They are pretending to fight Daesh," Yildirim said during a Tuesday address to members of the ruling party in parliament. "Turkey is the only country that is leading a fight. The United States isn't doing anything," Press TV reported.